"I may have been tipped off from a friend in the DEA. enough said. U.S. Customs is seizing ampules easier because they run suspected packages, letters or whatever over an ultrasound that is programmed to flag the density of glass. No kidding.

All elements/compounds have a density band . sound frequincies are constant.
So, a suspected package ( by the hundereds ) may get a quick ultrasound; but not too see inside. this takes WAY to much time/man power. but to get a quick 'red-light' of glass desity.. a constant. this further my plees with gear heads to e-mail thier suppliers in encrypted e-mail only, ways to camoflage ampules. inside a small lamp, wooden box, mixed in with crayons.... condoms... whatever.
I grew up with this agent. he's a good man. he hasn't seen the machine, but heard about it and it's success."

read on: (by the way, i studied this very subject while receiving my first physics degree)

"Ultrasound is widely used in health care for non-invasive diagnostics and in industry for non-destructive testing. It generates visual images from inside the test medium: the fetus, malignant tissue, stones, etc. in the human body. In the industrial applications, besides defect detection, ultrasound can also be used to determine significant materials characteristics such as density, thickness, mechanical properties, level sensing, and more. Knowledge of ultrasonically analyzed information is important for human health as well as for cost-effective production of quality industrial materials.
Ultrasound operates on the same principle as the other characterization methods also based upon wave- material interaction phenomena. These are: Optical, X-ray, infra-red, Raman spectroscopy, nuclear magnetic resonance, neutron, g-ray, mass spectrometry, etc. By propagating a wave in a given medium, useful information about the medium can be generated by analyzing the transmitted or reflected signals. Ultrasound differs from other wave-based methods because it does not require sample preparation; is non-hazardous; provides the means to determine mechanical properties, microstructure, imaging, & microscopy; is portable; and is cost-effective. Furthermore, ultrasound is applicable to all states of matter, with the exception of plasma and vacuum. Propagation of ultrasound in a material is not affected by its transparency or opacity. Table I provides a comprehensive introduction to ultrasound measurements and to the information revealed either directly or through correlation with measurements.

During the last twenty years, both ultrasound and its applications have grown phenomenally. Uses in industry have gone beyond overt defect detection in metals to include: characterization of elastic and mechanical properties; delaminations in multi-layered materials; proximity and dimensional analysis;
measurements of anisotropy and heterogeneity; surface profiling, chemical corrosion, crystallization and polymerization; liquid and gas flow metering; imaging of surface and internal features of materials; viscosity of liquids; texture and microstructure of granular and cellular materials; applied and residual stresses; high temperature, pressure, and radiation environment applications; robotics, artificial intelligence, and so on. These highly desirable applications of ultrasound have attracted the attention of a wide range of industries such as structural and electronic materials and components manufacturers, aircraft and aerospace, chemical and petroleum, plastics and composites, lumber and construction, highways and aircraft landing strips, bridges and railroads, rubber and tire, food, pharmaceutical, and on and on!"

"Scatterer sizes less than and equal to the wavelength
Consider a medium subjected to acoustic insonification, and a particle in this medium that is much smaller than the wavelength of the sound. If this particle is of the same density and compressibility as the medium, it scatters no sound at all. If its density is the same but its compressibility is different, it will react to the surrounding pressure variation by radially expanding and contracting differently than the surrounding medium. . The analytic solution for the radiation pattern from a spherical elastic scatterer in a fluid was first described by Faran[8]. The radiation pattern of such a scatterer is dependent on the material properties of the sphere and the medium and on the sphere's radius. Also, the result depends on whether one includes the effects of sound penetrating into the sphere and reverberating, which distinguishes the ``elastic'' from the ``inelastic'' solution."

peace,
msg

To answer the question above about the foil, basically there is no way to hide the gear bro. Now in the fied there are machines that operate over a "tunable" frequency spectrum and bandwidth. Operators can, when ever they feel the need tweak a machine to look through into the next layer of material. Not only do these things work in the ultrasonic range but also, infra red, ultra violet, X, K and other radar frequencies and some even border on visible light (human eye) range. Thats scary stuff because operating in reverse, meaning that the object itself could become an emitter of the very same frequency being tested, you could in effect make something invisible that is actually sitting right in front of you. This technology (3rd & 4th generation stealth) is exactly why the department of defense has canned the last few whiz bang bombers & fighters that contractors have built & proposed. OK I'm way off topic but it's some very cool shit! Long story short, you can't hide your gear, I'd lean toward making it a package they have no interest in anyway, I.E. the guts of something electronic, mechanical, organic etc.